Dating raised bogs: New aspects of AMS 14C wiggle matching, a reservoir effect and climatic change

Abstract

-High resolution AMS dating of Holocene raised bog deposits (Engbertsdijksvenen,The Netherlands) shows natural 14C variations (wiggles) which can be matched with the dendrochronological calibration curve. Comparison of our results with other, conventionally dated peat cores and the A14C record shows an unexpected and as yet unreported reservoir effect, and a QSR marked and sudden wetting of the bog surfaces coinciding with the advent of a SpGrer-type solar minimum (the Homeric minimum). The potential of AMS dating to vastly improve the accuracy of Holocene chronologies is demonstrated.

The multi-annual carbon budget of a peat-covered catchment

“…These RCA values have been reported fro a range of sites across northern peatlands, and rates of accumulation vary from a high of 88.6 gC/m 2 /yr (Tolonen and Turunen, 1996) to as low as 0.2 gC/m 2 /yr on Baffin Island (Schlesinger, 1990). There are recognised problems with this technique including: long-term anoxic decay in the catotelm ; reservoir effects (Kilian et al, 1995(Kilian et al, , 2000; poor estimates of peat bulk density; and short term changes in carbon accumulation will not be well represented (Hilbert et al, 2000). In order to resolve some of these issues the short-lived radioisotope 210 Pb has been used (e.g.…”

Radiocarbon dating of bulk peat samples from raised bogs: non-existence of a previously reported ‘reservoir effect’?

“…Indeed, Kilian et al (1995) found several published peat cores where sequences of bulk 14 C dates followed the shape of the 14 C calibration curve, but where the matches improved when a positive 14 C age offset was assumed for the peat bulk 14 C dates (see Fig. 1A-D).…”

“…These results were not expected; rootlets are generally believed to cause younger 14 C ages because they penetrate from higher, younger levels (e.g., Shore et al, 1995). Kilian et al (1995) then proceeded to see whether other peat cores could also possess unidentified 14 C reservoir effects.…”

“…orck et al, 1998). Kilian et al (1995Kilian et al ( , 2000 obtained a high-resolution sequence of 14 C AMS dates of selected plant remains from a peat core. Upon matching this sequence with the 14 C calibration curve ( 14 C wiggle-match dating; van Geel and Mook, 1989) it appeared that, when giving priority to placing pure Sphagnum samples on the calibration curve, Sphagnum samples containing some (2-4%) ericaceous rootlets floated ca.…”

“…750 to 400 cal BC when the 14 C calibration curve shows a plateau (approximately constant 14 C ages), preceded and followed by phases with rapidly changing 14 C ages. Such periods with pronounced shapes (especially plateaux) in the 14 C calibration curve offer the best possibilities for identifying reservoir effects in sequences of 14 C dates (Kilian et al, 1995).…”